Tube and plate heat exchangers are well known. Typically a hot fluid passes through a tube which has a number of plates or fins attached to it. Generally the plates or fins have a dimension of several times the diameter of the tube and the fins are spaced close together. The purpose is to transfer heat to the plate or fin by conduction and then have a fluid such as air extract the heat from the fluid by convection. The present invention does not use a finned heat exchanger.
U.S. Pat. No. 6,644,388 issued Nov. 11, 2003 to Kilmer et al., assigned to Alcoa Inc., discloses a sheet product which has improved heat transfer properties. The sheet has a number of textured features having a dimension from about 1 to 50 microns. Sheet can be used as fins on a heat exchanger or can be made into tubes. The tubes can be textured on the inside or on the outside. However there are fins on the exterior of the tube (Col. 4, lines 34 and 35). The patent teaches that pipe made from a rolled sheet is used in cooling applications such as radiators, heaters, evaporators, oil coolers, condensers and the like. The patent doesn't suggest the micro textures could be used on the surface of a pipe which is to be heated.
The paper “On Enhancement of Heat Transfer with Ribs” Applied Thermal Engineering 24 (2004) 43–57, discloses putting ribs on the surface of, for example, a fin. The heat transfer from the fin improves as a function of a number of factors including rib height and angle of inclination of the rib. However, the paper does not suggest ribs could be applied to the external surface of a pipe taking up heat from an environment.
The paper “Enhanced Heat Exchangers for Process Heaters” Published November 2001 by the Office of Industrial Technologies teaches the use of dimpled tubes in the convection section of a heat exchanger. The dimples produce a vortex effect which may increase heat transfer up to about 30% compared to a flat tube. The reference does not teach or suggest using ribs rather than dimples.
The present invention seeks to provide a simple solution to improving the heat transfer (up take) in a tube carrying a chemical to be process at elevated temperature such as tubes in the radiant section of an ethylene furnace.